Increasing concern with energy, environmental protection, and health factors have cooperated to enhance the potential of radiation curable compositions as adhesives. These adhesive compositions typically comprise a polymerizable mixture that can be applied as a thin film to a substrate and polymerized by exposure to a radiation source such as an electron beam, plasma arc, ultra violet light ("UV"), and the like.
Compositions which are curable under the influence of radiation in general, and ultra-violet light in particular, are well known. Unfortunately, these known compositions suffer from a number of disadvantages. For example, many of these compositions have insufficient flexibility that causes them to crack in use when applied to flexible substrates. Other compositions do not adhere sufficiently to substrates such as carbonates and metals with the undesirable result that the laminated layers become dislodged or peel. Still other compositions require use of solvents that must be evaporated during curing. Evaporation of such solvents increases production time, consumes energy and creates atmospheric pollution problems.
A need therefore continues for radiation curable adhesive compositions which remain homogeneous, which can be readily and uniformly applied to substrates and which show improved adherence to substrates such as carbonates and metals.